High tension cable



March l5, i932. M HCHSTDTER lfg HIGH TENSION CABLE Filed June 4, 1929 INVENTOR WTNS mmno1/mam @MKM BY Patented Mar. is, 1932 UNITED STATES PATENT ori-ICE MARTIN HCHSTDTER, 0F BRUSSELS, BELGIUM, ASSIGNOR T0 NAAMLOOZE VENNOOT SCHAP HANDEIMAATSCHAPPIJ CABLON (CABLON CORPORATION), 0F THE HAGUE,

NETHERLANDS HIGH TENSION CABLE Application led June 4, 1929, Serial No. 368,341, and in Germany January 6, 1928.

Applications have been filed in Germany, Jan. 6, 1926;.Canada, Nov. 13, 1926; Japan, Dec. 17, 1926 Holland, Nov. 1, 1926; Switzerland, Nov. 2, 1926; Czechoslovakia, Nov. 3, 1926; Norway, Oct. 28, 1926; Denmark, N ov. 1, 1926; Sweden, Oct. 30, 1926; Spain, Dec. 4, 1926; Austria, Oct. 27, 1926; Hungary, Oct. 28, 1926; Italy, Dec. 3, 1926; vEngland and ireland, Nov. 4, 1926; France, Nov. 10, 1926; Belgium, Dec. 17, 1926. A

The present application is in part a continuation of my prior application, entitled High tension cables, tiled December 27, 1926, Serial No. 157,400.

1" he reliability of an electric cable in service is increased with respect to the electric stresses if its insulating material is put under pressure. This has been attained by arranging tubes with permeable walls in the cable and separated from its electrical insulation, such tubes being it for receiving and conducting a liquid or gaseous pressure medium which at suitable places is put under pressure by external mechanical means.

rlhe` permeable walls permit a free and direct transmission of the hydrostatic pressure of the pressure medium to all points of the inner or outer surface of the core insulation, also a cable previously provided with the external protecting covering may be impregnated through these tubes. Certainditicultics, however, arise owing to the intimate connection between the pressure medium and the insulating material by this arrangement with permeable walls.

T he insulating impregnation material must be identical with the pressure medium, that is, it must be still liquid at the lowest working temperatures. 'I his is, however, for electrical reasons often undesirable. The tubes must also generally be evacuated in the factory before the cable is sent out. Consequently the core insulation loses entirely or partially its impregnating material, and therefore a second impregnation is neces sary after the cable is laid, which wastes time and is less reliable. Impregnation with the liquid pressure medium cannot easily be carried out previous to the application of the lead covering, that is to say the usual impregnation methods and the now generally adopted manufacturing apparatus cannot be made use of. Thel use of an impregnating material different from the pressure medium, for example a viscous liquid, is very difliicult because the two materials mix later,

The invention is based on the new experience that it is not necessary to maintain 'the pressure liquid in bodily contact with the il--- pregnating material of the insulation, but that the favorable edect of the pressure on the reliability of the cable in service is also obtained if an impermeable membrane is inserted between the pressure medium and the insulation. This membrane must, however, be suiiiciently flexible in order to allow a uniform transmission of the pressure from the pressure medium to the insulation at all points.

Therefore, according to the invention, impermeable flexible layers are provided between the actual insulating material and the channels for receiving and conducting the pressure medium in the cable. 1f tubes with permeable walls are used in the channels besides, this is only done for other, for example mechanical, reasons.

The accompanying drawings show several examples of cable according to the invention.

Figure 1 is a cross-section of a single core cable with an impermeable layer around 'the hollow copper conductor;

Figure 2 is a cross-section of a three core cable with metallized cores in which an impermeable layer (a membrane) isl provided around the hollow copper conductor of each core;

' on each side of the insulation, and with pressure fluid applied both inside and outside the core. t

The-sin le core cable as shown in Figure 1 consists o a metal conductor a, the insulation b and the lead covering e. The conductor a is hollow, the-inner space d serving as a pressure channel. The insulation b is separated from the metal conductor by a membrane The cable can be manufactured and laid in the usual manner, that is, the membrane o: is applied to the copper conductor a and the insulating material b is woundon and then the cable is impregnated with a suitable impreg nating material. The lead'covering e` is then applied.

The membrane :v can be formed in diii'erent ways, of one or more layers, so long as it satisfies the two-fold condition that it is suiliciently impermeable to the impregnating material in the insulation b and to the pressure medium in the channel l and is also sufiifore, consist of a conducting or of a non-conducting material; it can have the form of a` thin cylinder with or Without a seam, or the form of a wound tape. In the latter case a tape of paper or fabric is preferably selected which-is soaked with a synthetic resin or a similar substance. By this the tape and the membrane formed of it become impermeable also atv the overlapping edges of the tape, since the latter arercaused to adhere by the application of heat during the drying of the insulation b before its impregnation. In this way an impermeable layer is obtainedwhich adheres as a completely exible membrane to the inner surface of the insulation b since the membrane is practically composed of the same material (paper) as the insulation b.

After this cable has been manufactured in the known inanner it differs from an ordinary single core cable only by the inserted membrane and the hollow space cl. After it has been laid, the hollow space d can easily `be lled with the pressure medium, for exmedium, are preferably arranged at the cable terminal boxes.

Figure 2 shows the cross-section of a three core cable with metallizcd cores, in which every core is lconstructed as shown in Figure 1. f is the double iron tape armouring, g the eleetricall conductin layer of the outer surfaces of t e cores, w ch may, for example,

-be metallized by known processes, in order to prevent ionization. The latter metallizing is preferably permeable, in order to allow the core to be impregnated through it. h are the filling spaces which in the usual manner are filled with jute or other material. The whole of the cable within the lead is manufactured exactly as Figure 1in the usual manner, that is, the hollow copper conductors a are wound with Vthe membrane ai and the insulating material b, laid up together and with the material la in the dry state, impregnated, covered b the lead and armoured. The cable is lai and pressure applied similarly as indicated for the example described with respect to Figure 1.

The membrane a.' during the impregnation process prevents the impregnating material from penetrating into the channels d and in service any diffusion between the materials in and d. It transmits, however, the pres sure mechanically from d to b, by which th di-electric strength of the insulation b it raised.

Referring to the embodiment illustrated in Figure 3, the construction here is intended to illustrate one of many possible constructions in which the pressure iiuid exerts its pressure on the insulation,both inwardly and outwardly, through an impermeable but flexible membrane. The construction here chosen for illustration follows in general that illustrated in Figure 2, Vwith the exception that an additional impermeable and flexible membrane or layer w is applied around the insulation of each core, and the filling space is occupied by a second body of pressure fluid d.

In Figure 4 the sameprinciple bf applying pressure to both sides of the insulation is illustrated, as in Figure 3, but in this example, the construction is applied to a single stranded` core. The insulation b of the core is here shown as having the impermeable and flexible membrane on its inner surface, and' a similar impermeable flexible membrane m' on its outer surface. The inner pressure uid is shown at d, whereas the outer pressure iiuid d is disposed between the impermeable tlexible membrane w and the lead covering e, the pressure duid space between them being maintained by a spiral c of suliiciently i rigid material.

In the above described constructions the armouring f withstands the radial pressure exerted in the outward direction by the pressure medium. In the absence of armounng the lead covering e must eventually be made rendere suticiently resisting by alloying or otber= wise, so that it can withstand this pressure provided the cable is not drawn into tubes o' sucient resistance .l claim l. A high tension cable comprising a metal conductor, insulating material 'therefor9 a pressure :duid channel in said conductor9 a layer of impermeable and exible material between said conductor and said insulating material, and a pressure duid in said pressure uid channelo 2 A high tension cable comprising a nieta conductor, insulating material therefor9 a pressure iuid channel in said conc'luctcr9 an impermeable and exible layer consisting o a tape-like winding containing synthetic resins disposed between said conductor and said insulating material, and a pressure duid in said pressure duid channel.

3. A high. tension cable comprising a metal conductor, insulating material therefor, a pressure :duid channel in said conductor, an impermeable and exible layer in the forni of a thin cylinder disposed between said con ductor and said insulating material, and a pressure iuid in said pressure fluid channeln e. A high tension cable comprising a conduetor9 insulating material therefor, pressure iluid channels inside and outside said insulating material, a layer of impermeable and flexible material between each of said pressure duid channels and said insulating material, and a pressure :duid in each of said MARTIN HCHSTDTER.

. channels. 

